Ethyl ether of dextran



Patented Mar. 14, 1944 ETHYL ETHER OF DEXTRAN Grant L. Stahly, Columbus, Ohio, and Warner W. Carlson, Pittsburgh, Pa., assignors, by, mesne assignments, to Chemical Developments Corporation, Dayton, Ohio, a corporation of Ohio No Drawing. Application November 24, 1939, Serial No. 305,936

13 Claims. '(Cl. 260209) This invention relates to the production of polysaccharide materials by the action of various micro-organisms on suitable culture media, and to processes for converting these polysaccharides into their ether, mixed ether, ester, mixed ester or mixed ether-ester derivatives.

It is the object of this invention to produce polysaccharide materials by the action of various micro-organisms on suitable culture media and in particular to produce dextran; and to thereafter subject the polysaccharide materials such as dextran to a process of etherification or esteriflcation either while the materials are in the culture media or after separation therefrom so as to produce the new products of resinous character such as the benzyl ether of dextran, the butyl and ethyl ether of dextran, etc.

It is an object to utilize the known methods for preparing ethers and esters of polysaccharides other than dextran to produce these new materials.

The polysaccharides are produced by inoculating media containing sucrose, nitrogenous compounds and various salts with bacteria of known genus and species. These bacteria may be placed in one of two groupings, those that produce polysaccharides known as levans, or those that produce the polysaccharides known as dextrans. The two types of polysaccharides are distinguished from one another by the fact that on hydrolysis with acids or enzymes, the dextrans yield only dextrose while the levans yield only levulose. As specific examples, Bacillus mesentericus, B. subtz'lis, B. megatherium, Pseudomonas pram, Ps. prumcola or Ps. phaseolz' may be employed for the production of the levan type of polysaccharide, while Leuconostoc mesenteroides or L. dextranicum may be used for the production of the dextran type.

The culture media employed must contain some sucrose; this can be either refined or crude sucrose, molasses or any similar sucrose containing material. Nitrogen may be added in the form of commercial peptone, beef extract or other nitrogen containing material. If molasses is used as the sucrose source, nitrogenous compounds in sufiicient quantity are present in it so that none need be added. Salts such as dipotassium phosphate and sodium chloride are also added. As a specific example, a typical medium may contain: sucrose, -10 per cent, peptone, 0.1 per cent, dipotassium phosphate 0.2 per cent and sodium chloride 0.1 per cent. The pH of the medium preferably is adjusted to slightly on the alkaline side of neutrality,

The production of the polysaccharide is favored by keeping the reaction of the media slightly alkaline throughout theperiod of fermentation. This may be accomplished by the periodic addition of alkali to the fermenting media or by using an excess of calcium carbonate in the media. After inoculation the cultures are incubated at the temperature most favorable to the growth of the microorganism being used. For one of the preferred forms, Leuconostoc mesenteroides, this temperature is around 25 degrees C. The progress of the fermentation may be followed by periodically removing samples of the fermenting culture media and precipitating the polysaccharide contained in them by the addition of three to five times their volume of alcohol or acetone. The precipitated polysaccharide may then be weighed. When a maximum of polysaccharide has been formed the culture media are ready for the etherification or esterification processes. The length of time necessary for the maximum of polysaccharide to be formed will vary with the organism employed, the temperature of incubation, the concentration of sucrose and other factors.

The polysaccharide may be isolated from the solution by precipitation with alcohol or acetone. Preferably the reaction of the fermented medium is first adjusted to the neutral point to lessen the possibility of hydrolysis of the polysaccharide, and the solution then concentrated by evaporation to approximately one-fourth its original volume. The solution is then poured, with stirring, into three to five times its volume of alcohol or acetone. The polysaccharide may be precipitated directly from the fermented culture media by the addition of alcohol or acetone, but it is then necessary to use a considerably larger amount of the precipitating agent.

For the preparation of the ether and ester derivatives of these polysaccharides it is not necessary that they first be isolated from the culture media in which they were formed. Instead the necessary reagents may be added directly to the fermented media, and after completion of the reaction, the ether, ester, or mixed ether-ester derivatives can be recovered from the mixture, either by a simple mechanical process in case the product is water insoluble, or by the use of specific precipitating agents.

If, however, the polysaccharide is not removed from the culture solution befor esterification or etherification, the product obtained is a mixture of compounds. It will contain, besides the ethers and/or esters of the polysaccharide, the corresponding derivatives of any excess sucrose or metabolic products remaining in the fermented culture media. In some cases this may be desirable since a blending of these various derivatives yields a product with a range of solubilities. However, in cases in which a product with the specific properties of the polysaccharide derivative alone is desired, it is necessary either to separate the dextrans or levans from the culture media before chemical treatment, or else to removethe undesirable by-products, from the mixture obtained by the direct treatment of the fermented media, -by the use of specific solvents.

Whether the fermented media are treated directly, or the polysaccharides first isolated by alcohol or acetone precipitation, the proportions of the reactants used in the preparation of the ether derivatives are approximately as follows: one mol of the polysaccharide, 3.5 mols of the alhl or aralkyl halide and 4.5 mols of sodium hydroxide. If the polysaccharide was isolated from the medium before the chemical treatment.

- sufficient water must be added to the mixture so as to yield approximately a per cent solution of the sodium hydroxide.

The process of making the ether broadly involves alkylation which comprises the introduction of an alkyl radical by substitution or addition into the organic compound, in this instance dextran. There may be utilized for this purpose any one of a large number of alkyl radical containing compounds. The following are typical examples: methyl, ethyl, propyl, butyl, amyl, and

hexyl. Further the introduction of the aralkyl or benzyl radical as well as the unsaturated allyl group may be employed.

If the fermented culture medium itself is used, the amount of water present should be so regulated by concentration or dilution to again yield approximately a 10 per cent solution of the alkali. After addition of the reagents the mixture is heated for a predetermined time, usually 4 to 6 hours, at a temperature anywhere from 80 to 130 degrees C. This temperature depends on the derivative being prepared.

In general, the higher the temperature and the longer the period of heating the greater will be the number of hydroxyl groups in the polysaccharide which will be substituted by the ortemperature and time of heating employed is consequently governed by the type of product desired. The organic halide used may be any 46 ture media.

member of the aliphatic series such as methyl in color and soft-and rubbery in consistency.

chloride, ethyl chloride, propyl or isopropyl chloride, butyl chloride or any of its isomers, etc., or any one of the aralkyl series such as benzyl chloride.

The benzyl ethers are ble. used, increasing the proportion of halide to polysaccharide, running the reaction at a higher temperature and for a longer period of time will generally result in a decreased water solubility for the products obtained.

It is to be understood that the organic halide used may be either the chloride, bromide or iodide derivative. For purposes of economy, the chlorides are generally employed.

generally water insolu- At the conclusion of the reaction period excess halide is recovered by any suitable process such as steam distillation. The product is isolated by mechanical means if it is water insoluble or by precipitation if it is water soluble.

ous introduction of two or more organic halide compounds into the reaction'mixture, in which case the product will be a mixed ether; or a particular ether derivative may be prepared and the product from the reaction then treated with a diflerent organic halide to yield a mixed ether derivative. Again. an ether derivative may be prepared and then further treated with organic acid chlorides, acid' anhydride and the like for the preparation of mixed ether-ester derivatives. Such variations in treatment are, of course, almost without number.

The products in general are to be described as plastic, amorphous masses, either water soluble or insoluble depending upon the reaction conditions and the particular halide employed. As an example, the benzyl ether of dextran is a water insoluble material which resists the action of the common organic solvents.

The following are examples of specific practices of our method for the production of new products. It will be understood that we do not desire to be confined to the detailed proportions, temperatures and pressures, although we are reciting hereinafter those that we have found to be the preferred temperatures and other conditions.

It will be also understood that it is comprehended within this process the production of a large number of allied materials.

It will be further understood that we are illustrating the process and the materials that can be produced by typical materials within which wecomprehend other similar new materials.

Exam'rn I Benzyl ether derivatives This process may be carried out directly on the fermented culture media containing the polysaccharide, such as dextran, although the same process can be employed with the extracted dextran after it has been removed from the cul- This statement applies to the other examples hereinafter recited.

To a portion of the fermented culture medium in which the polysaccharide has been produced and in which there is approximately 30 gm. of

ganic radical of the halide compound used. The 0 th polysaccharide, is added 90 gm. of benzyl chloride and40 gm. of sodium hydroxide. The resulting mixture is heated for approximately five hours. If the temperature is held at to degrees C., the crude product is light orange when higher temperatures of from to degrees C. are employed, an orange-brown product is obtained of the same consistency but of greater resistance to solvents. The time of heat- Regardless of the type f rganic halide 60 mg may range from 4 to 6 hours but 5 hours is the preferable time. By varying the temperature of this benzylation process, the solubilities in various solvents of the resulting products are varied. These products are substantially insol- 05 uble in water.

' Exams: II

Bun/l ether derivatives To a portion of the fermented culture medium containing 30 gm. of dextran, we add gm. of butyl chloride and 40 gm. of sodium hydroxide. The mixture is heated at 100 degrees C. for four hours. The derivative is an amorphous The process may be varied by the simultane- 75 mass that is water soluble.

Exams: III

Mixed benzyl ether-butyl ether derivatives To a. water solution of the butyl ether derivative is added benzyl chloride and sodium hydroxide in the proportion of 30 gm. of the butyl ether; 90 gm. of benzyl chloride and 40 gm. of

sodium hydroxide. The mixture is heated at 80 Beta-hydro ethyl ether derivatives To a volume of the fermented culture medium containing about 30 gm. of dextran was added 160 gm. of ethylene chlorhydrin and 40 gm, of sodium hydroxide, and the reaction mixture heated at 80 to 85 degrees C. for five hours. At the end of this time the solution had become almost black in color, but on acidification a considerable amount of gas was given of: and the color changed to a light brown. Since the betahydroxy ethyl ether derivative is water soluble it was isolated by precipitation with acetone. The product was an amorphous, hygroscopic mass.

Exam V Mixed beta-hydromy ethyl ether-benzyl ether derivatives To a water solution of the beta-hydroxy ethyl ether derivative was added benzyl chloride and sodium hydroxide in the proportion 30 gm. of the ether, 90 gm. of benzyl chloride and 40 gm. of alkali. The mixture was heated at 80 to 85 degrees C. for five hours. After removal of excess benzyl chloride and benzyl alcohol by steam distillation, the resulting product appeared as a golden-brown, rather moist and stringy amorphous mass.

ExAmLa VI Ethyl dextran The preparation of ethyl dextran by the use of ethyl chloride as the ethylating agent may be efiected, but since ethyl chloride is a liquid boiling at about 8 degrees C. it is necessary to run the reaction under pressure. A mol ratio of ethyl chloride to dextran of 6:1 is used and the dextran is maintained in an aqueous alkaline solution while the reaction is carried on under a temperature of 135 degrees C. for about ten hours. After removal of excess ethyl chloride and ethyl alcohol by steam distillation as in the prior examples the resulting product is isolated 'as a soft resinous mass.

Ethyl iodide may be used as the ethylating agent for the preparation of ethyl dextran. In this instance a mol ratio of iodide to dextran of about 6:1 is used and the reaction carried out under reflux at 85 degrees C. for about four hours. Due to the low boiling point of ethyl iodide the reaction must be carried out at substantially low temperatures.

Diethyl sulphate may also be used as the ethylating agent for preparing ethyl dextran. Moi ratios of diethyl sulphate to dextran of 3: 1 to 6: 1 may be utilized. The ethylating agent is added to an alkaline solution of the dextran and the substances reacted together at a temperature under heat for about one and one-half hours during which time the reaction temperature is raised from 50 to 100 degrees C. The reaction is then continued at this last temperature for an additional one and one-half hours. The resultant product is found to be soluble in methyl alcohol, ethyl alcohol, cellosolve and acetone.

By reacting dextran in an alkaline solution with diethyl sulphate at a mo] ratio of 6:1 of diethyl sulphate to dextran and carrying out the reaction at degrees C. for eight hours and then increasing the temperature to degrees C. for twelve hours under reflux condenser, a water insoluble ethyl dextran separates out which is soluble in acetone, ethyl acetate and butyl acetate. This ethyl dextran product is of resinous consistency and can be utilized as a synthetic resin in the compounding of plastics and coating compositions similarly as in the case of benzyl dextran.

In the alkylation of dextran to produce ethyl dextran, it will be appreciated that other alkylating agents can be utilized in place 01' the alkyl halides, and alkyl sulphates which are the most commonly employed alkylating agents. Examples of other alkylating substances which may be utilized are triethyl phosphate, arylsulfonic alkyl esters such as the ethyl ester of p-toluenesulfonic acid and higher alkyl esters.

This application is a continuation in part of our copending application Serial No. 156,427, filed July 29, 1937.

It will be understood that the temperatures and times are relative and may be varied within reasonable limits to secure the objectives desired.

It will be further understood that we desire to comprehend within this invention such modifications as come within the scope of our claims and our invention.

Having thus fully described our invention, what we claim as. new and desire to secure by Letters Patent is:

1. As a new product, the ethyl ether of dextran.

2. As a new product, an alkylated reaction product of dextran comprising the ethyl ether thereof.

3. The method of making dextran ethyl ether which comprises reacting a fermented culture medium containing dextran with diethyl sulphate while maintaining the dextran in an alkaline solution.

4. The method of making ethyl ether of dextran which comprises reacting an aqueous alkaline solution of dextran with diethyl sulphate.

5. A process of making ethyl dextran comprising heating a mixture of dextran dissolved in an alkaline solution with diethyl sulphate in the moi ratio of diethyl sulphate to dextran of from 3:1 to 6:1 while heating the mixture and reacting the mixture together at a temperature of from 50 to 130 degrees C. for sufilcient time to produce the ethyl ether derivative of dextran.

6. The method of making dextran ethyl ether which comprises reacting a sodium hydroxide solution of dextran with an ethylating agent.

7. The method of making ethyl ether of dextran which comprises reacting a culture medium containing fermentable gummy polysaccharides of the formula (CsHioOs): with an ethylating agent in sodium hydroxide solution 8. The method of making ethyl ether of dextran which comprises reacting a culture medium containing gummy fermentable polysaccarides of the formula (CcHioOs): and an ethylating agent in sodium hydroxide solution at a. temperature of between 50 and 130 C.

9. The method 01' making ethyl ether of dextran which consists in reacting an aqueous sodium hydroxide solution of dextran with an ethylating agent.

10. The method 0! making ethyl ether of dextran which comprises reacting dextran with an ethyl halide in the mol ratio of halide to dextran of approximately 6:1 while maintaining the mixture in an aqueous solution containing sodium hydroxide.

11. Themethod of making the ethyl ether derivative of dextran comprising reacting dextran with an ethyl halide while the dextran is maintained in aqueous sodium hydroxide solution and heating the mixture at from 85 to 100' C. for about one hour. 7

12. The method of making ethyl dextran comprising heating a mixture of dextran dissolved in 5 an alkaline solution and an ethyl halide.

13. In the method of making the ethyl ether derivative of dextran, the step of reacting dextran in sodium hydroxide solution with an oathylating agent.

10 GRANT L. STAHLY.

WARNER W. CARLSON. 

